Laser light source, method for controlling dual color wheels of light source, and laser projection device

ABSTRACT

A laser light source is provided. The laser light source includes: a laser device; a first color wheel and a second color wheel, on both of which there are corresponding color regions, wherein the laser device emits laser which illuminates the first color wheel and the second color wheel sequentially, and exits from the color regions on the second color wheel; a first marker and a second marker arranged respectively on the first and the second color wheels; a first sensor configured to detect the first marker, and to generate a first sense signal; a second sensor configured to detect the second marker, and to generate a second sense signal; and a control unit configured to synchronize the first color wheel and the second color wheel.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit and priority of Chinese PatentApplication No. 201510739594.2 filed Nov. 4, 2015 and Chinese PatentApplication No. 201510738951.3 filed Nov. 4, 2015. The entiredisclosures of the above applications are incorporated herein byreference.

FIELD

The present disclosure relates to the field of laser light sources, andparticularly to a laser light source, a method for controlling dualcolor wheels of a light source, and a laser projection device.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

A laser light source, which is a solid-state light source, has become anoption of an emerging projection light source due to a series ofadvantages including high luminance, high efficiency, a long lifetime, agood color gamut, greenness, etc.

In an existing light source including laser and fluorescence generatedby excited fluorescent powder in the industry, blue laser is typicallyused as an excited light source of a laser projection system, and alsoas light in blue which is one of the primary colors including red,green, and blue. A fluorescence wheel is a wavelength conversion deviceconfigured to generate light in the other two primary colors than bluelight. In an implementation of the prior art, blue laser is emitted ontothe fluorescence wheel to excite blue fluorescent powder and yellowfluorescent powder so as to generate blue light and yellow lightrespectively, where the blue light and the yellow light passes a greenlight filter sheet and a red light filter sheet of a color filter wheel,thus resulting in green and red light, and blue laser is transmitteddirectly through the fluorescence wheel, and a transparent region of thecolor filter wheel without being filtered in color, and enters a lightpath system, so that the three primary colors including red, green, andblue are output from the color filter wheel as a result.

Moreover some yellow light is typically added to the system for higherbrightness, and the yellow right generated by the fluorescence wheel istransmitted directly through the transparent region of the color filterwheel, thus resulting in monochromatic yellow light, so that blue laserpasses the fluorescence wheel and the color filter wheel, thus resultingin the monochromatic light in the three respective primary colors, andthe monochromatic yellow light. Thus it is necessary to synchronize thefluorescence wheel with the color filter wheel so as to generate themonochromatic light in the three respective primary colors, where onlyone color is output through the color filter wheel in a timing period,for example, if blue light is output by the fluorescence wheel, then thecolor filter wheel will be rotated accordingly to the blue light filterregion; otherwise, different colors may be output and mixed with eachother, and thus altered, and the proportion of the three primary colorsmay also be varied, so that the three primary colors cannot be timed andoutput normally.

In the prior art, both of the wheels are synchronized typically in acoaxial design, and as illustrated in FIG. 1, a fluorescence powderwheel 11 and a color filter wheel 12 are connected coaxially, and lie intheir respective planes which are parallel to each and placed on anemitted light path of a laser light source 13; and in the dual colorwheels, color regions of the fluorescence powder wheel (includingfluorescent regions and transmission region, where the color of thetransmission region can be regarded as the color of laser transmittedthrough the transmission region) correspond to three color filterregions distributed on the color filter wheel, and the dual color wheelsare rotated in synchronization by driving them into rotation at somefrequency using the same motor 14.

In the design above, the boundaries of the same color region in thefluorescence wheel and the color filter wheel need to correspondprecisely to each other, that is, projections of the boundaries of thatcolor region in the two wheels onto the axis shall coincide with eachother. However this structure may be difficult to assembly in a process,and an offset error occurring in machining and installation will existall the time because the two color wheels and their wheel axes arefixed. Due to the phenomenon of color mixing due to this error, thepurity and the timing at which the colors are output typically have tobe guaranteed by removing those mixed components of two colors, whichcoincide with each other at by some angle, at the cost of lowerbrightness of the respective monochromatic light.

It is desirable to propose a method for controlling dual color wheels tobe synchronized so that the two wheels can be synchronized consistentlyeven if they are not coaxial.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

An object of the disclosure is to provide a laser light source, a methodfor controlling dual color wheels of a light source, and a laserprojection device so as to address the technical solution of controllingthe non-coaxial dual wheels to be synchronized.

The object of the disclosure is attained by the following technicalsolutions:

An aspect of the disclosure provides a laser light source including: alaser device; a first color wheel and a second color wheel, on both ofwhich there are corresponding color regions, wherein the laser deviceemits laser which illuminates the first color wheel and the second colorwheel sequentially, and exits from the color regions on the second colorwheel; a first marker and a second marker arranged respectively on thefirst color wheel and the second color wheel, wherein a position of thefirst marker on the first color wheel corresponds to a position of thesecond marker on the second color wheel; a first sensor configured todetect the first marker, and to generate a first sense signal; a secondsensor configured to detect the second marker, and to generate a secondsense signal; and a control unit configured to synchronize the firstcolor wheel and the second color wheel according to the first sensesignal and the second sense signal.

Another aspect of the disclosure provides a method for controlling dualcolor wheels of a light source, applicable to the laser light sourcedescribed above, the method including: detecting, by the first sensorand the second sensor respectively, the first marker and the secondmarker, and generating the first and second sense signals; andsynchronizing, by the control unit, the first color wheel and the secondcolor wheel according to the first sense signal and the second sensesignal.

The disclosure further provides a laser projection device including alaser light source including: a laser device; a first color wheel and asecond color wheel, on both of which there are corresponding colorregions, wherein the laser device emits laser which illuminates thefirst color wheel and the second color wheel sequentially, and exitsfrom the color regions on the second color wheel; a first marker and asecond marker arranged respectively on the first color wheel and thesecond color wheel, wherein a position of the first marker on the firstcolor wheel corresponds to a position of the second marker on the secondcolor wheel; a first sensor configured to detect the first marker, andto generate a first sense signal; a second sensor configured to detectthe second marker, and to generate a second sense signal; and a controlunit configured to synchronize the first color wheel and the secondcolor wheel according to the first sense signal and the second sensesignal.

Further aspects and areas of applicability will become apparent from thedescription provided herein. It should be understood that variousaspects of this disclosure may be implemented individually or incombination with one or more other aspects. It should also be understoodthat the description and specific examples herein are intended forpurposes of illustration only and are not intended to limit the scope ofthe present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a schematic structural diagram of the dual color wheels in thecoaxial design;

FIG. 2 is a schematic structural diagram of a laser light sourceincluding a laser element according to an embodiment of the disclosure;

FIG. 3 is a schematic diagram of a correspondence relationship between acolor wheel and a marker according to a first embodiment of thedisclosure;

FIG. 4 is a schematic diagram of another correspondence relationshipbetween a color wheel and a marker according to the first embodiment ofthe disclosure;

FIG. 5 is a flow chart of a method for controlling dual color wheels ofa light source, according to the first embodiment of the disclosure;

FIG. 6 is a waveform diagram of a first sense signal and a second sensesignal in the first embodiment of the disclosure;

FIG. 7 is a schematic diagram of the dual color wheels prior tosynchronization in the first embodiment of the disclosure;

FIG. 8 is a schematic diagram of the dual color wheels initiallysynchronized in the first embodiment of the disclosure;

FIG. 9 is a schematic diagram of a marker arrangement error in the firstembodiment of the disclosure;

FIG. 10 is a schematic comparative diagram of pulse signals of the dualcolor wheels corresponding to the marker arrangement error in the firstembodiment of the disclosure;

FIG. 11 is a schematic diagram of a voltage waveform of a third sensesignal in the first embodiment of the disclosure;

FIG. 12 is a block diagram of a system for controlling dual color wheelsof a light source, according to a second embodiment of the disclosure;

FIG. 13 is a schematic diagram of a laser projection device according toa third embodiment of the disclosure; and

FIG. 14 is a schematic structural diagram of dual color wheels in alaser light source in the third embodiment of the disclosure.

Corresponding reference numerals indicate corresponding parts orfeatures throughout the several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

The technical solutions according to the embodiments of the disclosurewill be described below in details with reference to the drawings.

First Embodiment

The disclosure is intended to provide a method for rotating non-coaxialdual color wheels in synchronization, applicable to a laser light sourcewith a non-coaxial design of the dual color wheels. The laser lightsource, the structure thereof as illustrated in FIG. 2, includes a laserdevice 0, a first color wheel 1, and a second color wheel 2, where thelaser device 0 emits laser which illuminates the first color wheel 1 togenerate fluorescence, and the laser and the fluorescence pass thesecond color wheel and exit from corresponding color regions on thesecond color wheel 2 respectively.

FIG. 2 illustrates an example of the positional and structuralrelationship between the non-coaxial dual color wheels, where drivingmotor shafts 12 and 22 are connected respectively with the first colorwheel 1 and the second color wheel 2 to drive their wheel surfaces torotate periodically. As illustrated in FIG. 2, there is an angle betweenthe extended center lines of the driving motor shafts 12 and 22, wherethe angle can be a sharp angle, a right angle, or an obtuse angle,although the extended center lines of the driving motor shafts 12 and 22are perpendicular to each other in this example. That is, the shafts ofthe first color wheel 1 and the second color wheel 2 are non-coaxial,and accordingly the planes where the wheel surfaces of the two wheels 1and 2 are not parallel in space but intersect at some angle. In theexample illustrated in FIG. 2, there is illustrated only one positionalrelationship between the first color wheel and the second color wheel,but the embodiment of the disclosure will not be limited thereto.

Here the first color wheel can be a fluorescence wheel on which thereare a green fluorescence powder region, a blue fluorescence powderregion, and a yellow fluorescence powder region (since red fluorescencepowder is excited inefficiently, it is replaced with the yellowfluorescence powder, but the yellow fluorescence powder can still bereferred to as the red fluorescence powder region because yellow lightfrom the yellow fluorescence powder is finally filtered into red light).The second color wheel can be a color filter wheel on which there are agreen color filter region, a blue laser transmissive region, and a redcolor filter region. The green color filter region, the blue lasertransmissive region, and the red color filter region are distributedrespectively on the color filter wheel at the same angles and orderswith the green fluorescence powder region, the blue fluorescence powderregion, and the yellow fluorescence powder region on the fluorescencewheel, where the red color filter region corresponds to the yellowfluorescence powder region, and is configured to filter yellowfluorescence from the yellow fluorescence powder into red fluorescence,so that the three primary colors including green, blue, and red areoutput sequentially from the color filter wheel.

Specifically a first marker 11 is arranged on the first color wheel 1,and a second marker 21 is arranged on the second color wheel 2,particularly on the side surfaces of the driving motor shafts of thefirst and the second color wheels. Moreover the positions of the firstmarker 11 and the second marker 21 on their respective color wheelscorrespond to each other. Since there are corresponding color regions onthe first color wheel and the second color wheel, typically thepositions where the first maker 11 and the second marker 21 are arrangedon driving motor shafts 12 and 22 are configured to correspond to somecolor region on their respective color wheels, so that it can be easilydetermined whether the two markers correspond in position to each other.In one particular embodiment, the starting position of the first maker11 on the side surface of the driving motor shaft 12, and the startingposition of the second maker 21 on the side surface of the driving motorshaft 22 are aligned respectively with the boundaries of the same colorregion on their respective color wheels. As illustrated in FIG. 3, forexample, if the starting position of a marker is aligned with theboundary of some color on a color wheel, then the boundary of that colorwill be a reference starting position for the marker on the color wheel.Particularly the starting position of the first marker 11 is alignedwith the boundary of the green region in the first color wheel 1, andthe starting position of the second marker 21 is aligned with theboundary of the green region in the second color wheel 2. Since thecolor regions in the color wheels are connected with each other, theboundary in this example refers to a boundary between two colors, and itcan be appreciated that the boundary is positioned as the boundarybetween the green region and the next color region. Those skilled in theart can appreciate and derive that the first marker and the secondmarker can alternatively be positioned at the boundaries between anyother two colors as long as the two colors on the first color wheel areas same as the two colors on the second color wheel.

Of course, in another particular embodiment, alternatively both of themarkers can be shifted by the same distance from the boundaries of thesame color, and as illustrated in FIG. 4, the two markers are shifted byan angle φ respectively from the boundaries of the green region on thetwo color wheels so that the positions of the two markers on the twocolor wheels also correspond to each other, and at this time, the radiallines shifted by the angle φ respectively from the boundaries of thegreen regions on the color wheels are the reference starting positionsfor the markers on the color wheels.

As also mentioned in the Background of the Disclosure, the first colorwheel and the second color wheel need to be rotated while theirrespective color regions correspond to each other, so that if the firstcolor wheel is rotated to the green region, then the second color wheelalso needs to be rotated to the green region (corresponding to the realfunction of filtering in green) so that the color of light exits fromthe second color wheel is green; otherwise, the colors may be mixed, andtheir timing may be altered out of order, so the three primary colorscannot be output normally.

A method for controlling the non-coaxial first color wheel 1 and secondcolor wheel 2 in the laser light source will be described below withreference to FIG. 5 together with FIG. 2.

As illustrated in FIG. 5, the method includes the following steps:

Step S11 is to detect the first marker and the second marker, and togenerate a first sense signal and a second sense signal.

In an embodiment of the method, the makers are black thin films or blackadhesive tapes or carbonized markers, where the black color absorbslight in effect, so during the rotation of the driving motor shaft, asignal transmitted by a sensor is absorbed by a black marker on the sidesurface of the shaft, and reflected back by a part of the side surfaceof the motor shaft where there is no marker, and thus detected by thesensor. Thus when the sensors detects the rotation states of the firstcolor wheel and the second color wheel, then the sensors can sense thepresence of the first marker and the second marker by the optical signaltransmitted by the sensors being absorbed and reflected, and to generatepulse signals at low and high levels, so that a first sense signalcorresponding to the first marker, and a second sense signalcorresponding to the second marker are obtained respectively in the samerotation periodicity.

Step S12 is to synchronize the first color wheel and the second colorwheel according to the first sense signal and the second sense signal.

Specifically, a rising edge or a falling edge of the first sense signaland the rising edge or the falling edge of the second sense signal inthe same rotation periodicity are compared to determine their timedifference, and the rotation speeds of the first color wheel and thesecond color wheel are adjusted so that the rising edge or the fallingedge of the first sense signal coincides with that of the second sensesignal to preliminarily synchronize the first color wheel and the secondcolor wheel.

The rotation periodicity here refers to the time taken for the two colorwheels to rotate by one round respectively. When the system is initiallystarted up, the two color wheels are accelerated at the same time and inthe same direction to the same rotation speed and then rotated at theconstant speed, so that the first marker and the second marker arestationary relative to each other, and then the first sense signalcorresponding to the first marker, and the second sense signalcorresponding to the second marker are generated in the same rotationperiodicity.

The first sense signal corresponding to the first marker includes arectangular pulse representing the rising edge and the falling edge ofthe first marker, and the second sense signal corresponding to thesecond marker includes a rectangular pulse representing the rising edgeand the falling edge of the second marker.

In one rotation periodicity, if the first color wheel and the secondcolor wheel have not been rotated in synchronization, then there may bea time difference between the rising edge or the falling edge of thefirst marker and that of the second marker, or there may be a timedifference between the first marker and the second marker passing thesame position.

As illustrated in FIG. 6, the first color wheel and the second colorwheel are rotated by one round, and there is a time difference betweenthe positions of the rectangular pulse corresponding to the firstmarker, and the rectangular pulse corresponding to the second marker, orthere is a time difference between the starting times of the two pulses,or there is a time difference between the ending times of the twopulses, so that the rising edge or the falling edge of the first sensesignal does not coincide with the rising edge or the falling edge of thesecond sense signal in time.

If there is a time difference between the rising edge or the fallingedge of the first sense signal and that of the second sense signal, thenthe rotation speeds of the first color wheel and the second color wheelmay be adjusted so that the rising edges or the falling edges of thefirst sense signal and the second sense signal coincide to preliminarilysynchronize the first color wheel and the second color wheel.Particularly as illustrated in FIG. 6, the time difference between thetwo markers of the two color wheels can be calculated from the firstsense signal corresponding to the first marker, and the second sensesignal corresponding to the second marker, and the circumference lengthdifference S between the two markers on the two color wheels can becalculated from the time difference as S=2πnRt, where n represents therotation speed, R represents the radius from the marker to the center ofthe color wheel, and t represents the time difference; and when the twocolor wheels are rotated at the same constant speed, then the two wheelsmay be stationary relative to each other, so the rotation speed of oneof the color wheels may be maintained, and the rotation speed of theother color wheel may be adjusted, thus decreasing the circumferencelength difference S between the two markers, i.e., the time differencebetween the two markers; and the adjustment time can be calculated inthe equation involving the rotation speed and the circumference length,and the circumference length difference S can be decreased to zero bycontrolling the adjustment time, so the time difference between the twomarkers may also be zero, and then the rotation speeds of the two colorwheels can be further adjusted to be the same constant speed at whichthey are rotated, so that the two color wheels can be synchronized. Herethe rotation speeds of the color wheels have been adjusted as describedabove merely by way of an example, but alternatively the rotation speedof one of the color wheels can be maintained, and the rotation speed ofthe other color wheel can be decreased; and the adjustment time can becalculated to decrease the circumference length difference to zero, andafter the difference has been adjusted, the two wheels can be furtherdriven at the same rotation speed.

It shall be noted that in the embodiment of the method, the first markerand the second marker are primarily configured as preset synchronizationposition markers, and also the rotation speeds of the motor shafts,i.e., the color wheels, can be calculated as a function of the numbersof pulse signals in the same rotation periodicity of the color wheels tothereby detect the rotation speeds of the color wheels. In this way, therotation speeds of the color wheels can be acquired in real time, andchanged by adjusting power of driver circuits, etc.

After the two color wheels are controlled to be synchronized in thesteps above, given the same position on the color wheels, the positionaldifference between the pulse signals of the markers of the first colorwheel and the second color wheel at the same instance of time asillustrated in FIG. 6 is adjusted so that the rising edges of the sensesignals of the markers corresponding to the two color wheels coincide asillustrated in FIG. 7, that is, the two markers are synchronized. Sincethe first and second markers correspond respectively to the sameposition on the first and second color wheels, the two color wheels arealso substantially synchronized. There are corresponding color regionsin the fixed order on the two color wheels, and when the color wheelsare substantially synchronized, then the same color regions of the twocolor wheels being rotated may also correspond to each other, so thatthey may match each other. For example, when the first color wheel isrotated to the green region, then the second color wheel may also berotated exactly to the green region, thus outputting green light. As aresult of the dual color wheels being synchronized, the light passes thesame color regions on the two color wheels sequentially in the sameperiod of time, thus guaranteeing the timing of the respective colorsamong the three primary colors finally output by the second color wheel.

However due to an assembly error, the positions of the first marker andthe second marker which are preset synchronization positions may not becompletely aligned with the reference starting positions on thecorresponding color wheels, e.g., the boundaries of the green regions inFIG. 3, or the position offset by the angle φ from the boundaries of thegreen regions in FIG. 4, but may be offset from the reference startingpositions by an order of millimeters or lower. As illustrated in FIG. 9,theoretical preset reference positions of the markers are the boundariesGL of the green regions, but the preset reference positions may beoffset by an angle φ1 from the original reference positions GL after thecomponents are assembled in reality, that is, the markers do notcompletely coincide with the theoretical preset positions after they areassembled, so the starting positions for the same color on the two colorwheels may not be completely synchronized either, and consequently thelight emitted by the two color wheels may still pass the different colorregions in the two color wheels being rotated while this offset isactive; and although the regions insignificantly overlap, the light inthe different colors may still be mixed. Additionally this offset maycause not only one of the colors to be mixed, but also the subsequenttwo colors to be mixed because the respective colors regions are fixedand correspond to each other so that such overlapping or displacementmay extend to the other two colors. As a result, if there is some error,then the three primary colors may be mixed in three periods of time inone periodicity.

In an embodiment, the step S13 can be further performed after the firstcolor wheel and the second color wheel are preliminarily synchronized,to thereby prevent the colors from being mixed due to this error so asto synchronize the color wheels more precisely.

The step S13 is to detect an optical signal in an output light path ofthe second color wheel, to generate a third sense signal, and tosynchronize again the first color wheel and the second color wheelaccording to the third sense signal, where the third sense signal is avoltage signal, the waveform of which corresponds to the optical signalin the different colors.

Since the light source finally output the light in the three primarycolors, the laser and the fluorescence are monochromatic light in thethree colors; since the sensor detects the optical signal in the outputlight path of the second color wheel, and generates the third sensesignal, the third sense signal is a voltage signal, which includes atleast three voltage values of different amplitudes and jumped voltagesat the boundaries between the colors; and since there are voltage jumpsat the boundaries between the colors because the markers are assembled,i.e., in the periods of time where the colors are mixed, the colorwheels can be synchronized again according to the output mixed colors.

In an embodiment, the step S13 particularly includes: step 1) theoptical signal is detected, and the third sense signal is generated;step 2) a period of time in which the value of the voltage of the thirdsense signal jumps is obtained; and step 3) the rotation speeds of thefirst color wheel and the second color wheel are adjusted until theperiod of time in which the value of the voltage jumps is below a presettime threshold, to synchronize again the first color wheel and thesecond color wheel. The detailed description is as follows.

Step 1) the optical signal is detected, and the third sense signal isgenerated.

Particularly after the color wheels are initially synchronized, sincethe first sense signal and the second sense signal correspondrespectively to the first marker and the second marker, when the risingedges of the two sense signal coincide, then the first marker and thesecond marker have been synchronized. However due to the assembly erroras illustrated in FIG. 9, after the markers are arranged, the firstmarker may not be completely aligned with the reference startingposition of the first color wheel, and the second marker may not becompletely aligned with the reference starting position of the secondcolor wheel, so that although the pulse signals of the markers aresynchronized, the reference starting positions of the two color wheelsmay not completely coincide at the same instance of time. As illustratedin FIG. 8, there is a variable time error t1 between the rising edgesignal of the first marker and the reference starting position of thefirst color wheel, and there is a variable time error t2 between therising edge signal of the second marker and the reference startingposition of the second color wheel, where both t1 and t2 are more thanor equal to 0, and when the error between the first marker and thereference starting position of the first color wheel is zero, that is,they are exactly aligned, then t1=0. If t2>t1, then there may be still avariable time error t2−t1 between the first color wheel and the secondcolor wheel after the first sense signal and the second sense signal areinitially synchronized. As illustrated in FIG. 10 as an alternative toFIG. 8, referring to the reference starting positions of the two wheels,if the dual color wheels being rotated shall pass these positions at thesame instance of time, then the pulse signals of the two markers may beinsignificantly misaligned, and there may be a time difference t2−t1,because the markers are offset from the reference starting positions dueto the assembly error. Although the error from the markers beingassembled lies in an allowable error range, the colors may overlap andthus be mixed in a color range, so for the sake of the colors which areoutput in reality, the reference starting positions of the first colorwheel and the second color wheel shall be adjusted so that they arealigned with each other at the same instance of time to thereby furthersynchronize the first color wheel and the second color wheel.

The second color wheel outputs the light in the three colors, and thesensor can detect the optical signal in the output light path of thesecond color wheel and obtain the voltage with at least three differentamplitudes, and the jumped voltage at the boundaries between the colorsdue to the error from the markers being assembled.

Particularly, the sensor generates a waveform diagram of the third sensesignal as illustrated in FIG. 11. The assembly-incurred error isembodied as the abnormally variation of voltage amplitude of the thirdsense signal, where the third sense signal is a voltage waveform signal,and the optical signal in the different colors has different brightnesswhich can be converted by the sensor into different voltage values, sothat the different voltage values in the third sense signal correspondto the different colors among the three primary colors; and since theamplitude of the voltage corresponding to any color light is a certainvalue, the amplitude of the voltage jumps between any two of the colors,and the mixed colors are embodied as the abnormally varying of thevoltage between the two colors.

Step 2) A period of time in which the value of the voltage of the thirdsense signal jumps is obtained.

The period of time in which the value of the voltage jumps refers to alength of time for which the amplitude of the voltage jumps abnormally.For example, the length of time t2−t1 of the abnormally jumping of thevoltage amplitude across the two colors can be determined from thewaveform as illustrated in FIG. 11, where the length of time of theabnormally jumping is the period of time in which the value of thevoltage jumps, and if t2−t1 (i.e., the period of time in which the valueof the voltage jumps) is shorter, then the two color wheels are moresynchronized, and if the period of time (t2−t1) is 0, then the two colorwheels are rotated in exact synchronization.

3) The rotation speeds of the first color wheel and the second colorwheel are adjusted until the period of time in which the value of thevoltage jumps is below a preset time threshold, to synchronize again thefirst color wheel and the second color wheel.

The color wheels can be adjusted particularly in the similar way thatthe first color wheel and the second color wheel are initially adjusted,that is, the time length t2−t1 as illustrated in FIG. 11 is determined,the current rotation speeds of the color wheels are known by countingthe numbers of pulses of the markers, and as know from the calculationequation above, the reference starting positions of the two color wheelsshall be aligned by adjusting the circumference length difference S, andthereafter the rotation speed of the second color wheel is adjusted withreference to the first color wheel, or the rotation speed of the firstcolor wheel is adjusted with reference to the second color wheel; andafter the circumference length difference between the two color wheels,or the time difference between the color wheels is decreased to 0, thetwo color wheels are adjusted into rotation at the same speed, so thatthe period of time in which the value of the voltage jumps is below thepreset time threshold, and thus the dual color wheels are synchronizedagain. In an embodiment, if the period of time in which the voltagejumps is 0, then the dual color wheels may be rotated in exactsynchronization, thus eliminating the abnormally jumping of theamplitude of the voltage across the two colors, and thus preventing thetwo color wheels from being out of synchronization due to the error fromthe markers being assembled.

In the embodiment above, firstly the first color wheel and the secondcolor wheel are initially synchronized so that the positions of themarkers of the two color wheels are synchronized, thus eliminating thetime difference in sequential order between the markers of the two colorwheels being rotated at the same speed, where if the rising edges oftheir pulses coincide, then the markers of the two color wheels havebeen synchronized. The color wheels are controlled to be synchronizedagain, to thereby prevent the different colors from being mixed witheach other due to the error between the markers assembled and thereference starting positions, which involves the second fine adjustmentmade taking into account the real colors emitted by the second colorwheel after the positions of the markers are synchronized, so that thedual color wheels are controlled to be synchronized precisely. Ascompared with the existing method for controlling coaxial dual colorwheels, the method for controlling non-coaxial dual color wheelsaccording to the embodiment of the disclosure can control the colorwheels to be initially synchronized, according to the sense signalscorresponding to the markers preset, i.e., the first marker on the firstcolor wheel, and the second marker on the second color wheel, and canalso eliminate the error from the markers being assembled, byeliminating the period of time in which the colors are mixed, the methodfor controlling color wheels to according to the disclosure is highlyflexible and can synchronize the dual color wheels precisely as opposedto the error arising from the same rotation speeds of the coaxial dualcolor wheels all the time in the prior art. Moreover it is not necessaryto prevent the two colors from being mixed as in the solution to thecoaxially connected dual color wheels, so the brightness of outputmonochromatic light can be improved, and also the purity of the colorsoutput by the color wheels, and the hue saturation of the image outputby the system can be improved. Also as opposed to the manual adjustmentmode, the method for controlling color wheels to be synchronizedaccording to the embodiment of the disclosure can not only save thelabor cost, but also eliminate the error in matching the colors, whichmay arise from different sensitivities of different persons to thecolors while adjusting manually the color wheel, so as to greatlyimprove the precision in matching the colors on the dual color wheels.

Moreover when the reference starting positions on the color wheels arelocated at the boundaries between the colors, then the startingpositions of the first marker and the second marker may also be alignedwith the boundaries of the same color on their respective color wheels,so that the extent of synchronization between the two markers can beevaluated according to the sense signals obtained by the sensors, andthe rising edges (if an active pulse is a pulse at a high level) or thefalling edges (if an active pulse is a pulse at a low level) of thepulses of the sense signals also represent the starting instances oftime of the color at the reference starting positions, so that thestarting color of the system can be known by determining the arrival ofthe pulse signals, and since the respective color regions and theirorder have been fixed on the color wheels, the timing of the colors ofthe system can also be known. For example, if the reference startingposition of the boundary of the green region of the first color wheel isthe boundary adjacent to the red region, then the starting position ofthe first marker will correspond to the boundary of the green region,and accordingly the starting position of the second marker will bealigned with the boundary of the green region of the second color wheel;and if the sensors detect the pulse sense signals of the first markerand the second marker, then the rising edges or the falling edges of thesense signal pulses will represent the beginning of the green color, andthe primary colors will be output in the order of green, blue, and red.In a real application, the markers can be aligned with the boundariesbetween the colors so that while the markers are sensed, the rotationspeeds of the color wheels can be measured and compared insynchronization, and also the starting instances of time of the colors,and their order can be determined. Thus if the dual color wheels aresynchronized, then the three primary colors can be timed and outputnormally.

It shall be noted that the above method for controlling color wheels hasbeen described as a method for controlling two color wheels to besynchronized only by way of an example, but if high illumination isrequired, then a number of sets of light sources may be arranged whilestructuring a number of color wheels or a number of sets of dual colorwheels, and the method for controlling color wheels to be synchronizedaccording to the embodiment of the disclosure will also be applicablethereto.

Second Embodiment

Further to the method above for controlling dual color wheels of a lightsource, an embodiment of the disclosure further provides a system forcontrolling dual color wheels of a light source, as illustrated in FIG.12, the system including a first color wheel 21 including a first maker(not illustrated), and a second color wheel 22 including a second marker(not illustrated), where the position of the first marker on the firstcolor wheel corresponds to the second marker on the second color wheel;and a first sensor 23, a second sensor 24, a third sensor 25, and acontrol unit 26.

Where the first sensor 23 is configured to detect the first marker ofthe first color wheel, and to generate a first sense signal, and is aninfrared sensor or an optical sensor; and the second sensor 24 isconfigured to detect the second marker of the second color wheel, and togenerate a second sense signal, and is an infrared sensor or an opticalsensor.

The control unit 26 is configured to synchronize the first color wheel21 with the second color wheel according to the first sense signal andthe second sense signal.

In an embodiment, the system for controlling dual color wheels furtherincludes: a third sensor 25 configured to detect an optical signal in anoutput light path of the first color wheel, and to generate a thirdsense signal which is a voltage signal, the waveform of the voltagesignal corresponding to the optical signal in the different colors, andthe third sensor 25 is an optical sensor or a luminance sensor andplaced in the output light path of the first color wheel; and in aparticular embodiment, the first color wheel is a fluorescence wheel,the second color wheel is a color filter wheel, and the third sensor isplaced in an output light path of the color filter wheel and configuredto obtain an optical signal in primary colors output by the color filterwheel as a result of color filtering. The control unit 26 is furtherconfigured to synchronize again the first color wheel and the secondcolor wheel according to the third sense signal.

In an embodiment, the control unit is configured to determine timedifference between a rising edge or a falling edge of the first sensesignal and that of the second sense signal in the same rotationperiodicity, and to adjust rotation speeds of the first color wheel andthe second color wheel so that the rising edge or the falling edge ofthe first sense signal coincides with the rising edge or the fallingedge of the second sense signal to preliminarily synchronize the firstcolor wheel and the second color wheel.

In an embodiment, the control unit is further configured to obtain aperiod of time in which a voltage value of the third sense signal jumps,to adjust rotation speeds of the first color wheel and the second colorwheel until the period of time in which the voltage value jumps is 0, tosynchronize again the first color wheel and the second color wheel.

Particularly referring back to FIG. 2 illustrating the schematicpositional and structural diagram of the dual color wheels, the firstcolor wheel 1 and the second color wheel 2 in FIG. 2 are equivalentrespectively to the first color wheel 21 and the second color wheel 22in the embodiment of the disclosure, and the first marker 11 and thesecond marker 12 in FIG. 2 are equivalent respectively to the firstmarker and the second marker in the embodiment of the disclosure.

The first marker and the second marker are preset synchronizationposition markers arranged respectively on the side surfaces of thedriving motor shafts of the first and the second color wheels 21, 22,and the markers can be black adhesive tapes or black thin films orcarbonized markers, where the black color absorbs light, so the rotationconditions of the first marker and the second marker can be known fromthe optical signal emitted by the sensors being absorbed and reflected,to determine the rotation conditions of the first color wheel and thesecond color wheel. The positions of both the first marker and thesecond marker can be aligned with the reference starting positions ontheir respective color wheel as illustrated in FIG. 3 or FIG. 4, so arepeated description thereof will be omitted here.

In a particular embodiment, the third sensor 25 is an optical sensorconfigured to convert a luminance signal into a voltage signal which isthe third sense signal, where the third sensor can embody intuitivelythe light output by the second color wheel in the form of voltage, andthe different colors have different luminance, so that the third sensesignal is output as a waveform signal with different voltage amplitudes.If the colors are mixed or overlap, then the amplitude of the voltagemay vary abnormally in a period of time because luminance signals of thelight in the different colors are mixed and converted into differentvoltage signals.

The method for operating the system has been described in details in themethod for controlling dual color wheels of a light source in the firstembodiment above, and if the system for controlling dual color wheelsaccording to the embodiment of the disclosure is applied, then itsoperating process will also bring the advantageous effects as describedin the first embodiment, so a repeated description thereof will beomitted here.

An embodiment of the disclosure further provides a laser light sourceincluding a laser device, and the system above for controlling dualcolors, where the laser device emits laser which illuminates the firstcolor wheel to generate fluorescence, and the laser and the fluorescenceexits from corresponding color regions on the second color wheelrespectively. Since the first color wheel and the second color wheel aresynchronized precisely after being synchronized twice, thus preventingthe colors from being mixed, after the light emitted by the laser devicepasses the first color wheel and the second color wheel, the threeprimary colors can be output sequentially from the second color wheelwithout affecting the luminance of the monochromatic light, so that thelight source with a high quality can be provided for an subsequentoptical device.

Third Embodiment

Further to the laser light source including the system above forcontrolling dual colors, an embodiment of the disclosure furtherprovides a laser projection device including the laser light sourceabove.

As illustrated in FIG. 13 showing a schematic diagram of the laserprojection device according to this embodiment, the laser projectiondevice includes a laser light source 1, an optical device 2, a lens 3,and a projection screen 4.

Here the laser light source including the system for controlling dualcolors according to the second embodiment can output sequentially lightin three primary colors, which enters the optical device 2 through anoptical rod (not illustrated), and the optical device 2 further includesa light path conversion element and a DMD (Digital Micromirror Device)chip (neither is illustrated) in addition to the structure of theoptical rod. The light in the three primary colors is modulated by theDMD chip, and then refracted again and again, and finally converged intothe lens 3.

The projection device in this third embodiment is a projection devicewith an ultra-short focus, which can be applied at home or portably, sothe lens 3 is a lens with an ultra-short focus, which is characterizedin that it can project an image with a high quality even at a lowprojection ratio. Light rays are modulated by the DMD chip and thenreach the lens 3, and finally are projected by a set of optical lenselements in the lens 3, including a number of convex lenses, concavelenses, non-spherical lenses, etc., onto the projection screen 4 to forma projected image.

Here as illustrated in FIG. 14, the laser light source 1 particularlyincludes a laser device 11, a first color wheel 15, and a second colorwheel 16; and in the embodiment of the disclosure, the laser device is ablue laser device emitting blue laser and operating as a excitationlight source to excite a fluorescence, where the first color wheel is afluorescence wheel, and the second color wheel is a color filter wheel.The color filter wheel 16 typically includes a first primary colorfilter region, a second primary color filter region, and a third primarycolor filter region, and in a particular embodiment, since the laser ishighly pure, a corresponding transparent region can be arranged on thecolor filter wheel to transmit the laser, and since the fluorescence isless pure than the laser, the fluorescence needs to be filtered in colorby the color filter in the corresponding color region to thereby furtherimprove the purity of the color; and the fluorescence wheel 15 includesa fluorescence region and a transmissive region, where the transmissiveregion is typically transparent glass configured to transmit the laserwhen the fluorescence wheel is rotated to the corresponding position,and the fluorescence region includes blue and yellow fluorescence powderregions (not illustrated) configured to receive the illuminating bluelaser, and to be excited to generate green fluorescence and yellowfluorescence. Here the green fluorescence region, the yellowtransmission region, and the yellow fluorescence region correspondrespectively to the green color filter region, the transparent region,and the red color filter region on the color filter wheel. In theembodiment of the disclosure, the fluorescence wheel 15 and the colorfilter wheel 16 are designed non-coaxially, and as can be apparent fromthe figure, the two color wheels are rotated in their planesperpendicular to each other, and although only a particular non-axialarrangement thereof has been illustrated in this embodiment, theembodiment of the disclosure will not be limited thereto.

In this embodiment, the fluorescence wheel 15 is a reflectivefluorescence wheel, and after the blue laser is transmitted in thetransmissive region of the fluorescence wheel 15, the blue laser furtherpasses a set of relay lenses arranged on the backside of thefluorescence wheel, including a first lens 12, a second lens 13, and athird lens 14 as illustrated in FIG. 14, where these optical lensesinclude planar reflective lens, convex lens, diffusive lens, and otheroptical lens, and they form a route along which the blue laser isreturned to the front side of the fluorescence wheel, is incident ontoan optical mirror 17, and combined with the excited fluorescence.

After the light in the three primary colors is combined, the lightfurther passes the color filter wheel 16 sequentially, and particularlypasses sequentially the positional regions in the corresponding colorson the color filter wheel, so that the light in the three primary colorsis output sequentially and reaches the optical device behind the laserlight source to provide illumination.

After the regions in the corresponding regions on the two color wheelscorrespond to each other, for example, if the central angle of the greenfluorescence region on the fluorescence wheel 15 is 108 degrees, thenthe central angle of the green color filter region on the color filterwheel may also be set accordingly to 108 degrees, the two color wheelswill be further rotated in synchronization so that they are keptstationary relative to each other.

In order to enable the fluorescence powder wheel and the color filterwheel to be rotated in synchronization, the embodiment of the disclosurecan be implemented using the method and the system according to thefirst and second embodiments above: as illustrated in FIG. 2, the firstcolor wheel 1 corresponds to the fluorescence wheel 15 in FIG. 14, andthe second color wheel 12 corresponds to the color filter wheel 16 inFIG. 14; and a first marker and a second marker are arrangedrespectively on the fluorescence wheel and the color filter wheel, andthe position of the first maker on the first color wheel corresponds tothe position of the second maker on the second color wheel.

A first sensor is arranged around the fluorescence wheel to detect thefirst marker, and to generate a first sense signal, and is an infraredsensor or an optical sensor; a second sensor is arranged around thecolor filter wheel to detect the second marker, and to generate a secondsense signal, and is an infrared sensor or an optical sensor; and acontrol unit of the laser device is configured to compare a rising edgeor a falling edge of the first sense signal with that of the secondsense signal in the same rotation periodicity; and to adjust rotationspeeds of the fluorescence wheel and the color filter wheel according tothe time difference between the rising edge or the falling edge of thefirst sense signal and that of the second sense signal so that therising edge or the falling edge of the first sense signal can coincidewith that of the second sense signal, thus initially synchronizing thecolor wheels. In an embodiment, the laser light source further includesa third sensor placed at the exit side of the color filter wheel, and isan optical sensor or a luminance sensor configured to detect an opticalsignal, and to generate a third sense signal which represents a detectedluminance of the light output by the color filter wheel, i.e., a voltagewaveform signal, where optical signal in different colors correspond todifferent voltage values; and the control unit of the laser projectiondevice is configured to obtain a period of time in which the voltagevalue of the third sense signal jumps abnormally, and to adjust therotation speeds of the fluorescence wheel and the color filter wheeluntil the period of time in which the voltage value jumps abnormally isbelow a preset time threshold, so that the fluorescence wheel and thecolor filter wheel are synchronized again. In an embodiment, if therotation speeds of the fluorescence wheel and the color filter wheel areadjusted until the period of time in which the voltage value jumpsabnormally is 0, then the fluorescence wheel and the color filter wheelare controlled to be synchronized precisely.

The first marker and the second marker are preferably black adhesivetapes or black thin films or carbonized markers affixed or spray andcoated on the side surfaces of the driving motor shafts of thefluorescence wheel and the color filter wheel.

After the fluorescence wheel and the color filter wheel are synchronizedtwice so that they are synchronized precisely, the light in the threeprimary colors output by the color filter wheel will not be mixed in anyperiod of time so that the luminance and the purity of the outputmonochromatic light can be improved, and further the hue saturation ofthe colors can be improved; and also the timing of the three primarycolors can be guaranteed so that the optical device 2 can be providedwith the light source with a high quality to thereby improve thecapability to render the colors of the projected image and the qualityto display the projected images in the colors.

In summary, in the laser projection device according to the embodimentof the disclosure, the first color wheel, i.e., the fluorescence wheel,and the second color wheel, i.e., the color filter wheel, are arrangednon-coaxially, the first marker and the second marker are arrangedrespectively at the corresponding positions on the fluorescence wheeland the color filter wheel, the first sense signal as a result ofsensing the first marker, and the second sense signal as a result ofsensing the second marker in the same rotation periodicity are obtainedrespectively by the first sensor and the second sensor, the rising edgesor the falling edges of the first marker and the second marker in thetwo sense signals are compared, the time difference between the risingedge or the falling edge of the first sense signal and that of thesecond sense signal is determined, and the rotation speeds of the drivermotors driving the fluorescence wheel and the color filter wheel areadjusted to eliminate the positional difference (i.e., time difference)between the two sense signals, so that the first marker and the secondmarker corresponding to the non-coaxial fluorescence wheel and colorfilter wheel are initially synchronized. Since there may some errorsbetween the first marker and the second marker, and the preset referencestarting positions of their respective fluorescence wheel and colorfilter wheel while they are assembled, the reference starting positionsof the two color wheels may not be completely aligned at the sameinstance of time due to the assembly error even if the two markers aresynchronized, so that there may be temporally inconstant timing, andthus the colors of the light output by the second color wheel may bemixed in some period of time. Accordingly the third sensor can bearranged in the output light path of the color filter wheel to obtainthe third sense signal which is a voltage signal, where the light in thedifferent colors correspond to different voltage, and the amplitudes ofthe voltage corresponding to the light in the two colors jump; and theabnormal voltage occurring while the optical signal in the two colors isjumping corresponds to the period of time in which the different colorsare mixed, so the rotation speeds of the two color wheels can beadjusted again to eliminate the abnormal voltage occurring while thevoltage is jumping, so as to enable the two color wheels to be rotatedin exact precision.

As compared with the prior art, the solutions according to theembodiments of the disclosure can prevent completely the two colors frombeing mixed at their boundary to thereby improve the precision ofsynchronization, and since it is not necessary to adjust the colorwheels to thereby eliminate the mixed colors, the luminance and thepurity of the optical signal output by the light source can be improved,and the timing at which the light in the three primary colors is outputcan be guaranteed.

It shall be noted that in the embodiments of the disclosure, theoperating process of the laser light source has been described by way ofan example in which the light source emits the monochromatic light inblue to excite the fluorescence power in two colors so as to generatethe fluorescence in the two colors, but the light source canalternatively be a dichromatic laser light source, where the laser lightsource in each color excites fluorescence power in one or two colors sothat light in the three primary colors can be generated as a result. Anoperating process of the latter light source similar to the operationprocess in the disclosure above can readily occur to those skilled inthe art, so a repeated description thereof will be omitted here.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

The invention claimed is:
 1. A laser light source, comprising: a laserdevice; a first color wheel and a second color wheel, on both of whichthere are corresponding color regions, the first color wheel including afluorescence wheel, the second color wheel including a color filterwheel, wherein the laser device emits a laser which illuminates thefirst color wheel and the second color wheel sequentially, and exitsfrom the color regions on the second color wheel; a first marker and asecond marker arranged respectively on the first color wheel and thesecond color wheel, wherein a position of the first marker on the firstcolor wheel corresponds to a position of the second marker on the secondcolor wheel; a first sensor configured to detect the first marker, andto generate a first sense signal; a second sensor configured to detectthe second marker, and to generate a second sense signal; and a controlunit configured to synchronize the first color wheel and the secondcolor wheel according to the first sense signal and the second sensesignal.
 2. The laser light source according to claim 1, furthercomprising: a third sensor configured to detect an optical signal in anoutput light path of the second color wheel, and to generate a thirdsense signal which is a voltage signal, a waveform of the voltage signalcorresponding to an optical signal in different colors; and the controlunit further configured to synchronize again the first color wheel andthe second color wheel according to the third sense signal.
 3. The laserlight source according to claim 1, wherein the control unit isconfigured to determine a time difference between a rising edge or afalling edge of the first sense signal and that of the second sensesignal in a same rotation periodicity, and to adjust rotation speeds ofthe first color wheel and the second color wheel so that the rising edgeor the falling edge of the first sense signal coincides with that of thesecond sense signal to synchronize the first color wheel and the secondcolor wheel.
 4. The laser light source according to claim 2, wherein thecontrol unit is configured to obtain a period of time in which a voltagevalue of the third sense signal jumps, and to adjust rotation speeds ofthe first color wheel and the second color wheel until the period oftime in which the voltage value jumps is below a time threshold, tosynchronize again the first color wheel and the second color wheel. 5.The laser light source according to claim 1, wherein the first markerand the second marker are located respectively on side surfaces ofdriving motor shafts of the first color wheel and the second colorwheel.
 6. The laser light source according to claim 1, wherein both thefirst marker and the second marker are black adhesive tapes or blackthin films or carbonized markers.
 7. The laser light source according toclaim 1, wherein both the first marker and the second marker are alignedwith boundaries of same color regions on their respective color wheels.8. The laser light source according to claim 1, wherein both the firstsensor and the second sensor are infrared sensors or optical sensors. 9.The laser light source according to claim 2, wherein the third sensor isan optical sensor or a luminance sensor.
 10. A method for controllingdual color wheels of a light source, applicable to the laser lightsource according to claim 1, the method comprising: detecting, by thefirst sensor and the second sensor respectively, the first marker andthe second marker, and generating a first sense signal and a secondsense signal; and synchronizing, by the control unit, the first colorwheel and the second color wheel according to the first sense signal andthe second sense signal.
 11. The method according to claim 10, furthercomprising: detecting, by a third sensor, an optical signal in an outputlight path of the second color wheel, and generating a third sensesignal which is a voltage signal, a waveform of the voltage signalcorresponding to an optical signal in different colors; andsynchronizing, by the control unit again, the first color wheel and thesecond color wheel according to the third sense signal.
 12. The methodaccording to claim 10, wherein synchronizing the first color wheel andthe second color wheel according to the first sense signal and thesecond sense signal comprises: determining time difference between arising edge or a falling edge of the first sense signal and that of thesecond sense signal in a same rotation periodicity; and adjustingrotation speeds of the first color wheel and the second color wheel sothat the rising edge or the falling edge of the first sense signalcoincides with that of the second sense signal to synchronize the firstcolor wheel and the second color wheel.
 13. The method according toclaim 11, wherein synchronizing again the first color wheel and thesecond color wheel according to the third sense signal comprises:obtaining a period of time in which a voltage value of the third sensesignal jumps; and adjusting rotation speeds of the first color wheel andthe second color wheel until the period of time in which the voltagevalue jumps is below a time threshold, to synchronize again the firstcolor wheel and the second color wheel.
 14. The method according toclaim 12, wherein adjusting the rotation speeds of the first color wheeland the second color wheel until the period of time in which the voltagevalue jumps is below the time threshold comprises: determining acircumference length difference between the first marker and the secondmarker; adjusting the rotation speed of the second color wheel or thefirst color wheel with reference to the first color wheel or the secondcolor wheel so that the circumference length difference between thefirst marker and the second marker is decreased to zero; and adjustingthe second color wheel or the first color wheel into rotation at a samespeed as the first color wheel or the second color wheel so that theperiod of time in which the voltage value jumps is below the timethreshold.
 15. A laser projection device, comprising a laser lightsource, wherein the laser light source comprises: a laser device; afirst color wheel and a second color wheel, on both of which there arecorresponding color regions, the first color wheel including afluorescence wheel, the second color wheel including a color filterwheel, wherein the laser device emits a laser which illuminates thefirst color wheel and the second color wheel sequentially, and exitsfrom the color regions on the second color wheel; a first marker and asecond marker arranged respectively on the first color wheel and thesecond color wheel, wherein a position of the first marker on the firstcolor wheel corresponds to a position of the second marker on the secondcolor wheel; a first sensor configured to detect the first marker, andto generate a first sense signal; a second sensor configured to detectthe second marker, and to generate a second sense signal; and a controlunit configured to synchronize the first color wheel and the secondcolor wheel according to the first sense signal and the second sensesignal.
 16. The laser projection device according to claim 15, furthercomprising: a third sensor configured to detect an optical signal in anoutput light path of the second color wheel, and to generate a thirdsense signal which is a voltage signal, a waveform of the voltage signalcorresponding to an optical signal in different colors; and the controlunit further configured to synchronize again the first color wheel andthe second color wheel according to the third sense signal.
 17. Thelaser projection device according to claim 15, wherein the control unitis configured to determine time difference between a rising edge or afalling edge of the first sense signal and that of the second sensesignal in a same rotation periodicity, and to adjust rotation speeds ofthe first color wheel and the second color wheel so that the rising edgeor the falling edge of the first sense signal coincides with that of thesecond sense signal to synchronize the first color wheel and the secondcolor wheel.
 18. The laser projection device according to claim 16,wherein the control unit is configured to obtain a period of time inwhich a voltage value of the third sense signal jumps, and to adjustrotation speeds of the first color wheel and the second color wheeluntil the period of time in which the voltage value jumps is below atime threshold, to synchronize again the first color wheel and thesecond color wheel.